This invention is directed to a system and method for performing color corrections on color image data. More particularly, this invention is directed to a system and method for performing color corrections on color image data in a primary color system. This invention is particularly useful in performing color corrections on color image data that is to be output on a image processing apparatus.
Device profiles or the like are typically used to translate color data created on one device into another device's native color space. A color space is typically a particular model of colors, represented by a tri-dimensional map. There are three broad classes of devices, input devices, display devices and output devices. For each device class; a series of base algorithmic models are described that perform a transformation between color spaces. The models provide a range of color quality and performance results equating to different trade-offs in memory footprint, performance and image quality.
A color model that describes each color in terms of the quantity of each secondary color, cyan, magenta, yellow, and black is commonly referred to as the CMYK color model. The CMYK system is used for printing. For mixing of pigments, it is better to use the subtractive colors, since they mix subtractively. In addition, although black could be obtained by mixing these three in equal proportions, in four-color printing, black is typically used as a separate colorant. The K in CMYK stands for ‘Key’ or ‘blacK,’ so as not to cause confusion with the B in RGB (Red, Green, Blue) color model.
As will be known in the art, the difference between the two color models is based on how color is produced. Red, green, and blue are projected light and cyan, magenta, yellow, and black is reflected light. Combining varying amounts of red, green and blue will faithfully create the spectrum of colors. By varying the amounts of red, green and blue, an image may be projected onto the phosphors of a monitor or television screen. However, pigments added to paper, successively, will darken the paper. Using selective light colors will recreate the spectrum on white paper. Thus, cyan will absorb red, magenta will absorb green and yellow will absorb blue. These are called the subtractive primary colors, or secondary colors. Because of the lightness of cyan, magenta and yellow, black, is used for the gray components.
Often the color conversion from one color space to a second color space is not flawless and there are errors in the quality, intensity, lightness, or other features of the second color space. For example, the CMYK printing materials for use in an image processing apparatus are not perfectly complementary colors of RGB, and will often generate solid blue colors that contain too much purple color.
The subject invention remedies the aforementioned problems and provides a mechanism which performs color corrections on color image data, especially in a primary color system.